An optical system, including off-axis ellipsoidal mirrors, suitable for application in the present invention is described in U.S. patent application Ser. No. 09/346,253, entitled xe2x80x9cDisplay System Having a Light Source Separate from a Display Devicexe2x80x9d.
Not Applicable
1. Technical Field
This invention relates to an optical apparatus suitable for use with a flowing fluid containing biological cells and more specifically to flow cytometry, the measurement of the fluorescence and light scattering of individual biological cells and other types of microscopic particles.
2. Background Art
As described in Steen, U.S. Pat. No. 5,684,575, a flow cytometer is an instrument for measurement of the fluorescence and light scattering of individual biological cells and other types of microscopic particles.
Hogg et al., U.S. Pat. No. 4,189,236, teaches the placement of a biological sample within an enclosed reflector cavity where part of the cavity is removed in order to facilitate placement of a focusing mirror. A limitation of the Hogg approach is that it requires a high numerical aperture (NA) for both the sensor and the excitation source. Also, the Hogg apparatus requires complex coupling optics and only has a single sensor port.
Ultraviolet (UV) light is known to be useful to disinfect fluids such as air and water by killing of bacteria, viruses and other pathogens. Specifically, ultraviolet (UV) light with a wavelength of between 100 nanometers (nm) to 280 nm, known in the art as xe2x80x98UV-Cxe2x80x99, is known to be germicidal. UV-C light is known to deactivate the deoxyribonucleic acid (DNA) contained within bacteria, viruses and other pathogens thus destroying their ability to multiply and cause disease. UV-C light with a wavelength of approximately 260 nm provides the highest germicidal effectiveness.
For most water borne pathogens, exposure to UV-C light with an energy flux of 20 milliwatt-seconds/cm2 is adequate to deactivate 99 percent of these pathogens. The World Health Organization (WHO) has a recommended standard of performance for an acceptable water disinfecting system that requires the processing of contaminated water containing 100,000 colony forming units (CFU) of e-coli bacteria per 100 ml of water and producing outlet water with less than one CFU per 100 ml. Guidelines for Drinking Water Quality, vol. 1, World Health Organization, Geneva, Switzerland, 1993, pg. 135.
The traditional approach in UV disinfecting systems is to use low-pressure mercury discharge lamps (i.e. fluorescent lamp without the phosphor). These lamps provide relatively low intensity energy flux, therefore to handle high fluid flow rates many such lamps are required along with large volume fluid storage tanks.
There is a long felt need in the art of flow cytometry for improved detection sensitivity, such as when there are but a few biological cells present in the flowing fluid. In addition, there is a long felt need in general for a safe and reliable method of disinfecting drinking water for human consumption using ultraviolet radiation.
My invention is a flow cytometer device where a fluid a fluid flows through this device and is illuminated by light or other radiation. The interaction with the flowing fluid and the light is detected by sensors within the flow cytometer. More specifically, my invention is directed toward an optical system making up part of the overall flow cytometer device.
The optical system according to my invention provides several unique enhancements to traditional flow cytometry. Advantageously, my inventive apparatus increases the collection efficiency of the fluorescent energy, for example from a biological cell, thereby enhancing the signal/noise ratio of a detected signal. A flow cytometer according to my invention can use simple sensors, such as photo-multiplier tubes (PMT), or imaging-based sensors such as charge-coupled devices (CCD) and can also provide a full 360 degree view of the specimen, potentially leading to a three dimensional capability.
The optical system according to my invention can additionally be used to disinfect a flowing fluid such as water by focussing ultraviolet light on the flowing fluid and thereby killing biological cells contained in the fluid.